The objective of this research is to derive an understanding of the cellular and molecular mechanisms which participate in the IgE (reagenic antibody) response in humans. Initially this will entail the definition of an optimal in vitro system for the synthesis of IgE using lymphocytes obtained from peripheral blood or tissues such as tonsil or lymph node. Various mitogens and antigens will be evaluated for their ability to stimulate IgE production in vitro. A sensitive double antibody radioimmunoassay will be used to quantitate the small amounts of IgE synthesized in culture. The effects of various immune cell populations (T lymphocyte, macrophage, etc.) on IgE production will be assessed. This will be accomplished through experiments using separate B and T lymphocyte populations. Such populations will be subjected to experimental manipulation and then re-combined in culture under defined conditions and the IgE produced by such cultures determined. This approach will allow for identification of the functional intercellular regulatory interactions which participate in the IgE response. This will be followed by experiments designed to functionally and serologically identify subpopulations of IgE regulatory immune cells. The nature of the interactions between the regulatory cells will be compared/contrasted to similar interactions regulating IgE production in vitro. At the same time, the nature of the precursor cell for IgE production and its relationship to IgG precursor cells will be investigated through cell depletion experiments directed at cell surface isotypes. Subsequently, we will attempt to produce soluble regulatory cells. Such soluble factors will allow for the isolation, identification and characterization of the mode(s) of action of the molecules which mediate the cellular interactions responsible for modulation or regulation of the IgE response.